This invention relates to a molded submersible motor particularly suitable for use in a well, having an improved electrical connector arrangement for interconnecting the power cable leads, the stator coils and an encapsulated starting switch unit.
A conventional submersible motor of the "canned" type has thin cylindrical metal liners of stainless steel rigidly fitted to the inner and outer circumferences of the stator, with liquid for lubricating the motor bearings filling the inner metal liner surrounding the rotor. While the canned type motor provides excellent electrical insulation for the stator coil, it requires a number of additional components such as flanges for securing end brackets or caps and for sealing the openings between both metal liners fixed to the stator. The brackets must be machined to close tolerances to enable watertight joints with the metal liners, which results in increased machining steps and manufacturing cost.
There has also been provided a molded type motor as disclosed in U.S. Pat. No. 4,015,154 to ostensibly eliminate the above-mentioned disadvantages of the canned motor. Such a molded motor gives rise to other problems, however, in that since the starting switch is embedded in the molded structure of the motor frame it is very difficult to replace or repair the starting switch unit, which is subject to frequent on-off operations and thus liable to become defective.
To overcome these problems a molded motor as shown in FIGS. 1 and 2 has been proposed which comprises a hollow cylindrical frame 5 formed of resinous molding material into which a stator structure having stator cores 2 and coils 3 is molded. End brackets 8 also formed of resinous molding material are detachably secured to the frame to close the end openings thereof. A starting switch 12 for the motor is molded into one of the end brackets, and may easily be removed and replaced if it fails. There are still some drawbacks with such a construction, however, in that it is necessary to provide additional connectors 15, 16 and 17, other than the main connector 6, for coupling the starting switch 12 housed in the end bracket to the stator coils 3. In addition, the frame 5 and end bracket 8 must be precisely molded to close tolerances and the connectors accurately positioned therein to enable the correct assembly of the bracket to the frame.